1. Field of the Disclosure
The present invention relates generally to power supplies and, more specifically, the present invention relates to a switched mode power supply.
2. Background
All electronic devices use power to operate. A form of power supply that is highly efficient and at the same time provides acceptable output regulation to supply power to electronic devices or other loads is the switched-mode power supply. In many electronic device applications, such as for example the low power off-line adapter/charger market, during the normal operating load range of the power supply an approximately constant output peak power is desired over a range of input voltage values.
For instance, a typical flyback power supply may be designed to operate from worldwide mains voltages such as for example 85V ac to 265 V ac. In many instances, it is a goal to design a power supply to deliver a maximum specified output power at all input voltages between a minimum specified input voltage and a maximum specified input voltage. For a given output power, the highest current in a power switch in a switched mode power supply occurs at the minimum input voltage. Therefore, the current limit for the switch and the values of other components in the power supply are selected to deliver the specified output power at the minimum input voltage. The power supply typically operates in continuous conduction mode at low input voltages to obtain the most power for a given current limit and component values.